Radio receiver



Dec. 15, 19,42.. E. F. ANDREWS 2,304,871.

` RADIO RECEIVER Filed Feb. '5, 1941 iw QM-EM Patented Dec. 15, 1942 RADIO RECEIVER Edward F. Andrews, Chicago, lll.

Original application July 18, 1938, Serial No.

219,713, now Patent No.

ber 11, 1941.

2,262,218, dated Novem- Divided and this application February 3, 1941, Serial No. 377,096

(Cl. Z50-20) 7 claims.

This invention relates to devices for tuning radio receivers in which tuning is effected by power means adapted to be set in operation by manually actuated means and adapted automatically to be rendered inoperative when the receiver has been tuned to the carrier wave of a broadcasting station received with suii'icient strength, and is a division of my copending application Serial No. 219,713, filed July 18, 1938, which issued on November 11, 1941, as Patent No. 2,262,218. I call this general type of station selection stop-oncarrier tuning. The manually actuated means comprises means controlling the change of an electric current or voltage and may be located at a point remote from the receiver. For example, it may be a manually actuated switch which is preferably located in remote relation to the receiver, being connected thereto by means of a cable.

The invention is very advantageous for tuning all varieties of radio receiver. It facilitates remote control and provides simple automatic tuning which does not require manual adjustments for setting up pre-selected stations.

The invention is very advantageous for effecting automatic tuning for automobile or other portable radio receivers where the receiver may be moved out of the vicinity of certain broadcasting stations and into the vicinity of others. As the form of automatic tuning of this invention will tune in the stations whose carrier waves are of suicient strength to cause stoppage of the power means driving the tuning element, it is not necessary to re-set the device to tune in a new set of stations when the geographical location of the receiver is changed. The device automatically tunes in the stations broadcasting carrier waves of suiiicient strength, regardless of what particular stations they may be, within the tuning range of the receiver.

As-tuning from one station to another is ef. fect'ed merely by pressing a button, the tuning operation may be performed by the driver of an automobile without taking his eyes from the road. He may simply continue to operate the tuning button until he hears the desired station. Y

This greatly enhances the safety of radio receiver operation by the driver of an automobile. As only a button or switch connected to the receiver by two small flexible wires is required for performing the tuning operation, this can be very conveniently mounted directly on the steering column, where the driver may operate it without. taking his hand from the wheel, while `the re-V ceiver may be mounted at any other suitable location in the automobile.

The invention is, of course, also adapted to the automatic tuning of stationary or home types of receivers, and also may be remotely operated in other lways. Also, many of `the featuresY described in connection with automobile sets are similarly advantageous for home receivers.

This invention relates particularly to means for securing the proper timing and for narrowing the electrical impulses which cause automatic stoppage on the carrier to effect more exact and uniform tuning. It relates, further, to an arrangement wherein the selectivity of a'tuned circuit forming part of-the receiving circuit is rendered sharp during tuning and broadened during reception to give a sound output of high delity and also to an arrangement utilizing the electron tubes and a tuned circuit normally utilized in the receiver, so that no additional tubes or .separate tuned circuits are necessary to effect the desired control of the tuning means. Certain features of this invention are also applicable to receivers tuned manually. t

The invention will be readily understood from the following description of an embodiment thereof taken in conjunction with the accompanying drawing, the single figure of which is a wiring diagram illustrating my invention and so much of a radio receiver as is necessary to understand the invention.

Referring now to the drawing, the tubes I 0 and II are intermediate frequency tubes. The tube I2 is a second detector and rst audio tube, while the tube I3 isan audio frequency amplifier. As already indicated, the drawing is intended to illustrate only part of the radio receiver so in actual practice and as disclosed in my copending application, the tube III would be preceded by a radio frequency amplifying tube, and if the receiver is of the superheterodyne type, a first detector and oscillator tube and tuning condensers operable by power means, to be referred to hereinafter, for tuning the receiver to the carrier signals of radio stations. Likewise, the tube I3 would be connected to a loudspeaker in a manner well known to those skilled in the art. y

The plate of tube I0 is connected to a primary I4 of a transformer I5. The tuned secondary I6 of this transformer is loosely coupled to the primary I4, and connected to the grid 'of tube II and to the leaf I1 of a multi-switch I8. The secondary I6 is also connected to an auxiliary windingv I9, which is closely coupled to the primary I4. The winding I9 is connected to a leaf of the multi-switch I8. The plate of the tube II is connected through a relatively closelycoupled transformer 2I to the diode plates of the tube I2. The primary of nected to a pole 22 of the multi-switch I8. The secondary of the transformer 2I is connected through a resistor 23 to the cathodes of the tube I2. The secondary of the transformer 2l and the resistor 23 are connected through a resistor 24 to a po-le 25 of the multi-switch a resistor 26 to the grid of the tube I0. 21 of the multi-switch I8 is connected to the `grid of tube I3. The leaf 28 of the multi-switch I8 is grounded. The pole 29 of the multi-switch I8 is connected through an plied with current from a transformer 32,"whic`h may be windings on the power transformer of the A. C. radio receiver. The motor 3I and switch 33V may be of thetype described in my aforementioned copending application, that is, the motor is so constructed and arranged as to declutch itself from the tuning condensers when deenergized and to beclutched thereto when energized, and the reversingswitch 38 is actuated from one of its two positions to the other by limit switch mechanism operated at the limits of movement of the condensers.

The leaf 33 of the multi-switch I8 is grounded, the leaf 34 is connected to the B supply, and the leaf 35 is connected through a winding 36 of a relay 31 to the B supply. The leaf 35 is also connected through a resistor 38 and a normally open, manually operable switch 39 to ground.` Y

The poles 25, 21, 29 and 22 are mechanically connected to the amature 40 of the relay.31. When `the relay is deenergized, the armaturev 40 Y ist moved away from the relay by a spring 4I,

is in contact with leaf I1,

with the result that the pole the leaf 20 and is separated from the the pole 21 is separated from the leaf 28, 29 is separated from the leaf 33, and the pole 22 is in contact with the leaf 34 and is separated from the leaf 35.- When the relay 31 is energized, it attracts the armature .49, with the result that the pole 25 is separated fromrthe leaf 20 and is in engagement with the leaf I1, the pole 21 is in engagement with the leaf 28 the pole 29 is in engagement with the leaf 33, and the pole 22 is Yseparated from the leaf 34 and'is in engagement with the leaf 35. The leaves 20 and I1 are biased so that they follow the pole 25 when it moves from one position to Vthe other so as to insure the engagement of the pole with the second leaf before it separates from thev rst leaf. The leaves 34 and 35 are similarly biased towards the pole 22,. Consequently, one of the leaves I1 and 20 is in contact with the pole 25 at all times, and one or other of the leaves 34 and`35 is in contact with the pole 2.2 at all times.

y The operation is as follows: When energy is supplied to the set, if the same is tuned to a station, that station will be received. If the switch 39 .is closed, the relay 31 is energized by B current flowing through the winding36, the. resistor 38 and the switch 39. Consequently, the pole 29 is brought into engagement with leaf 33, and the motor operates and remains in operation so long as the switch 39 is held closed. When the relay 31 is thus energized, the pole 21 is in engagement with the leaf 28, and the grid of the tube I3 is grounded so that the set remains mute. If the switch 39 is now allowed to open, or if it had been merely depressed momentarily, the relay 3111etransformer 2I is con- '.automatic reversing switch 39 to a reversible motor 3I which is Sup- 1 the pole,

IB and throughr` The pole ksequently, the plate current quite high. When, g strength is received,

of the grid of the tube vand the plate `current of the tube II is strongly densers. While the motor is operating after the relay 31 is energized by through the winding 36,

switch 39 is opened, the the iiow of B current leaf 35, pole 22 and the plate of tube II. Owing to the fact that no station is being received, there is little voltage drop across the resistor 23. Conof the tube II is however, a signal of sufficient a voltage drop is applied thaty the negative bias II is strongly increased across the resistor 23 so decreased so that the relay 31 opens. Y

It mayhere be noted that when a station is tuned in andthe relay 31 is deenergized, the grid circuit includes the windings I6 and I9 in series. Since the winding I9 is closely coupled tothe winding I4, the transformer I5.is more ibroadly tuned so as to provide for the passage of a signal of desired characteristics for audible Vreproduc-` tion. When, however, the motor is operating, the winding I9 is cut out by the separation of pole 25 from the leaf 29, and, consequently, the effective coils of the transformer I5 are the primary I4 and secondary I6. These windings vare loosely coupled so that the selectivity zof theY circuits is considerably increased. In other words,` the form of the resonance curve for each station is rendered more narrow and more accurate tuning is thereby obtainedfor stop-'on-carrier foperation. When the relay 31is deenergized inresponse to the reception of Va carrier signal, the

closely coupledwinding I9 is again introduced Y into the grid circuit of the tube II.' 1

It will be noted that the double throw switch, which includes the pole 22 and the leaves 34: and 35, provides a locking system which prevents `the operation of the motor in the event that the station received fades, or indeed goes on the air; The only mannerV in which the motor `maybe again put into operation is. by the closing ofthe switch 39. It will, however, a locking effect may be obtained by providing the armature 40 with suilicient movement away from the relay 31 so that it cannot be attracted by any energization of the relay 31 other than the strong energization provided by the closing the relay winding 36 and the resistor 38` directly to theplate circuit of the tube 2i. Although the invention has beenjdescribed- `in connection with the specific details of `a preferred embodiment thereof, it` must be understood such details are not intended to be limitative of the inventionexcept in, so far asset forth inthe accompanying claims. *A

Having thus described my invention, I ,declare that what I intendv to claim is:

1. In a radio receiver having a tuned circuit with a broad selectivity curve, at least one ,grid controlled radio frequency amplifying tube. and a power actuated means for operating tuning means, in combination, means including a device. responsive to the plate current of` said tube for be understood that stopping said tuning means when a carrier signal is closely tuned in, and means including a. circuit controlled in response to the plate current of said tube for increasing the selectivity of said tuned circuit during operation of said tuning means.

2. In a radio receiver having a tuned circuit tube for substantially simultaneously rendering said power means elective to oper-ate said tuning means and said selectivity increasing means to increase the selectivity of said tuned circuit.

3. In a radio receiver having variable tuning means, in combination, relay means for stopping said tuning means, an electron tube having a plate circuit connected to said relay means and a grid controlling the plate current for operating said relay means to stop said tuning means, a tuned circuit in said receiver through which the signal producing the sound output of said receiver passes, means including a rectifier energized by the signal after passage through said tuned circuit adapted to apply a rectiiied control voltage to said grid for operating said relay means to stop said tuning means when .a carrier signal is closely tuned in, and means associated with said tuned circuit and controlled by said relay means for reducing the selectivity of said tuned circuit when said tuning means is stopped.

4. In a radio receiver having variable tuning means, in combination, power means driving said tuning means, relay means operable to stop and start said power and tuning means, anelectron tube having a plate circuit connected to said relay means and a grid controlling the plate current for operating said relay means to stop said tuning means, a tuned circuit in said receiver through which the signal producing the sound output of said receiver passes, means including a rectier energized by the signal after passage through said tuned circuit adapted to apply a` rectified control voltage to said grid for operating said relay means to stop said tuning means when a carrier signal is closely tuned in, and means associated with said tuned circuit and controlled by said relay means for increasing the selectivity of said tuned circuit when said tuning means is started and 'decreasing the selectivity of said tuned circuit when said tuning means is stopped. k

5. In a radio receiver having variable tuning means, in combination, power means driving said tuning means, relay means operable to stop and start said power and tuning means, an electron tube having a plate circuit connected to said relay means and a grid controlling the plate current for operating said relay means to stop saidk tuning means, a tuned circuit in said receiver through which the signal producing the sound output of said receiver passes, means including a rectier energized by the signal after passage through said tuned circuit adapted to apply a rectified control voltage to said grid for operating said relay means to stop said tuning means when a carrier signal is closely tuned in, means associated with said tuned circuit and controlled by said relay means for increasing the selectivity of said tuned circuit when said tuning means is started and decreasing the selectivity of said tuned circuit when said tuning means is stopped, and means actuable by an operator for operating said relay means to restart said power and tuning means.

6. In a radio receiver as claimed in claim 4, wherein said electron tube, tuned circuit and rectifier constitute elements of a radio receiver used for the reproduction of audible signals.

7. In a radio receiver as claimed in claim 4, wherein the rectier is the rectier supplying an automatic volume control voltage to an amplifying tube of said receiver. l

EDWARD F. ANDREWS. 

